JP2022160356A - Frequency characteristics measurement device - Google Patents

Abstract

To provide a frequency characteristics measurement device capable of easily measuring frequency characteristics of a DUT at low cost.SOLUTION: A frequency characteristics measurement device includes: a calibration unit 3 configured to perform SOLT calibration at a cable end surface; a first measurement unit configured to measure an S parameter of a first substrate on which a DUT is mounted after SOLT calibration by the calibration unit 3; a second measurement unit configured to measure the S parameter of a second substrate that has a structure in which a portion on which the DUT is mounted from the first substrate is removed after SOLT calibration by the calibration unit 3; and an extraction unit 5 that is configured to extract the S parameter of the DUT by performing vector calculation on measurement results of the first measurement unit and measurement results of the second measurement unit. The extraction unit 5 regards reflection at a second substrate end surface of each of first fixture and second fixture obtained by virtually dividing the second substrate into two at a center as less than reflection at an end surface of the second substrate when it is not virtually divided into two at the center.SELECTED DRAWING: Figure 1

Description

The invention disclosed in this specification relates to a technique for measuring frequency characteristics of a DUT (Device Under Test).

The frequency characteristic of the DUT is measured by a frequency characteristic measuring device such as a vector network analyzer. In a conventional general measurement method, SOLT (Short-Open-Load-Thru) calibration described in Non-Patent Document 1 is first performed on the cable end surface. Then, remove the part where the DUT is mounted from the board with the Short instead of the DUT, the board with the Open instead of the DUT, the board with the Load mounted instead of the DUT, and the sample board with the DUT mounted. SOLT calibration is performed by sequentially attaching the Thru boards between the cables. After that, the S-parameters of only the DUT are extracted from the measurement results of the S-parameters of the sample board on which the DUT is mounted. Thereby, a pure DUT frequency characteristic can be obtained.

Kotomi Ichikawa and Yuichi Ichikawa, "Detailed explanation of S-parameters for high-frequency circuit design", 5th edition, CQ Publishing, January 1, 2020, pp.14-143

However, the conventional general measurement method described above requires four types of calibration substrates, and thus has the problem that the calibration substrates require a great deal of cost and the calibration work takes a long time.

The frequency characteristic measuring apparatus disclosed in this specification includes a calibration unit configured to perform SOLT calibration on the end surface of a cable, and a first substrate on which a DUT is mounted after the SOLT calibration by the calibration unit. a first measurement unit configured to measure an S-parameter; a second measurement unit configured to measure an S-parameter of a second substrate after the SOLT calibration by the calibration unit; and the first measurement. an extraction unit configured to extract the S-parameters of the DUT by performing a vector operation on the measurement results of the second measurement unit and the measurement results of the second measurement unit, the extraction unit configured to extract the second substrate from the Reflection at the end surface of the second substrate of the first fixture and the second fixture, which are obtained by virtually dividing the fixture into two at the center The first board has a structure in which at least one connector is provided on each of the first end face and the second end face, and the second board removes the portion where the DUT is mounted from the first board. and through-connection is performed by selecting arbitrary two connectors from all the connectors provided on the first substrate, and the number of the second substrates is equal to all the connectors provided on the first substrate. This is the configuration (first configuration) that is the total number of combinations in which two connectors are selected.

In the frequency characteristic measuring apparatus having the first configuration, the extractor extracts the amplitude of the S parameter indicating the reflection of the first fixture at the end surface of the second substrate by a single value over the entire frequency range of the measurement range. is a first fixed value, the phase of the S parameter indicating the reflection at the second substrate end surface of the first fixture is set to zero over the entire frequency range of the measurement range, and the second The amplitude of the S-parameter indicating the reflection at the substrate edge is set to the first fixed value over the entire frequency range of the measurement range, and the phase of the S-parameter indicating the reflection at the second substrate edge of the second fixture is set to , may be set to zero over the entire frequency range of the measurement range (second configuration).

In the frequency characteristic measuring apparatus having the first or second configuration, the extraction unit assumes that the transmission characteristics of the first fixture and the transmission characteristics of the second fixture are symmetrical (third configuration ).

In the frequency characteristic measuring apparatus having the first or second configuration, the extraction unit does not consider the transmission characteristics of the first fixture and the transmission characteristics of the second fixture to be symmetrical (fourth configuration).

In the frequency characteristic measuring device having any one of the first to fourth configurations, the distance between the two end faces to which the cable of the second board is connected is less than twice the reciprocal of the lowest frequency in the measurement range (the second 5 configuration).

A computer program disclosed in this specification includes a calibration unit configured to perform SOLT calibration at a cable end face, and S parameters of a first substrate on which a DUT is mounted after the SOLT calibration by the calibration unit. and a second measurement unit configured to measure S-parameters of a second substrate after the SOLT calibration by the calibration unit. A computer program for processing the measurement results of, comprising: a computer comprising: a first acquisition unit for acquiring the measurement results of the first measurement unit; Functioning as an extraction unit configured to extract the S-parameters of the DUT by performing a vector operation on the measurement result of the first measurement unit and the measurement result of the second measurement unit, the extraction unit Reflection at the end surface of the second substrate of each of the first fixture and the second fixture obtained by virtually dividing the two substrates into two at the center is The first board has a structure in which at least one connector is provided on each of the first end face and the second end face, and the second board is mounted with the DUT from the first board. A portion is removed, and any two of the connectors provided on the first substrate are selected and through-connected, and the number of the second substrates is equal to the number of the connectors provided on the first substrate. This is a configuration (sixth configuration) that is the total number of combinations in which two connectors are selected from all the connectors.

According to the invention disclosed in this specification, the frequency characteristics of a DUT can be easily measured at low cost.

FIG. 1 is a block diagram showing a schematic configuration of a frequency characteristic measuring device according to one embodiment. FIG. 2 is a schematic diagram showing a schematic structure of the first substrate. FIG. 3 is a schematic diagram showing a schematic structure of the second substrate. FIG. 4 is a flowchart illustrating an operation example of an extraction unit. FIG. 5 is a diagram schematically showing the S-parameters of the first fixture. FIG. 6 is a diagram schematically showing the S-parameters of the second fixture. FIG. 7 is a diagram schematically showing S parameters of the second substrate.

FIG. 1 is a block diagram showing a schematic configuration of a frequency specific measurement device according to one embodiment. A frequency characteristic measuring device 10 (hereinafter abbreviated as “frequency characteristic measuring device 10”) according to one embodiment shown in FIG. 1 is a vector network analyzer.

A frequency characteristic measuring device 10 includes a first port 1 , a second port 2 , a calibrating section 3 , a measuring section 4 and an extracting section 5 .

The first port 1 is configured to be connectable with one end E11 of the first coaxial cable CX1. The second port 2 is configured to be connectable with one end E21 of the second coaxial cable CX2.

The calibration unit 3 is configured to perform SOLT calibration on the cable end face. Specifically, the first port 1 is connected to one end E11 of the first coaxial cable CX1, and the second port 2 is connected to one end E21 of the second coaxial cable CX2. It is configured to perform SOLT calibration on each of the end face of the other end E12 of the cable CX1 and the end face of the other end E22 of the second coaxial cable CX2. Since the SOLT calibration on the cable end surface is a well-known technique disclosed in Non-Patent Document 1, for example, detailed description thereof is omitted here. The calibration unit 3 provides the calibration result to the measurement unit 4 .

The measurement unit 4 measures S parameters. The measurement unit 4 functions as both a first measurement unit and a second measurement unit.

The first measurement unit is configured to measure the S-parameters of the first substrate SUB1 (see FIG. 2) on which the DUT is mounted after SOLT calibration by the calibration unit 3 . That is, when the first measuring section performs measurement, the first substrate SUB1 is connected to the frequency characteristic measuring device 10 via the first coaxial cable CX1 and the second coaxial cable CX2.

The second measurement unit is configured to measure the S parameter of the second substrate SUB2 (see FIG. 3) having a structure obtained by removing the DUT-mounted portion from the first substrate SUB1 after SOLT calibration by the calibration unit 3. be done. That is, when the second measuring section performs measurement, the second substrate SUB2 is connected to the frequency characteristic measuring device 10 via the first coaxial cable CX1 and the second coaxial cable CX2.

FIG. 2 is a schematic diagram showing a schematic structure of the first substrate SUB1. FIG. 3 is a schematic diagram showing a schematic structure of the second substrate SUB2. The first substrate SUB1 has a portion P1 on which the DUT is mounted, a first fixture P2, and a second fixture P3. The second substrate SUB2 has a first fixture P2 and a second fixture P3. In the second substrate SUB2, the first fixture P2 and the second fixture P3 can be obtained by virtually dividing the second substrate SUB2 into two at the center.

The first fixture P2 has a first connector CN1 connectable to the other end E12 of the first coaxial cable CX1. The first connector CN1 is provided at the left end of the first fixture P2. The second fixture P3 has a second connector CN2 connectable to the other end E22 of the second coaxial cable CX1. A second connector CN2 is provided at the right end of the second fixture P3. The first fixture P2 and the second fixture P3 have bilaterally symmetric structures. However, the first fixture P2 and the second fixture P3 may not have completely bilaterally symmetrical structures, and may have slight manufacturing variations.

The extraction unit 5 is configured to extract the S-parameters of the DUT by performing vector operations on the measurement results of the first measurement unit and the measurement results of the second measurement unit. The extraction result of the extraction unit 5 may be stored, for example, in a portable storage medium detachable from the frequency characteristic measuring device 10, or may be displayed on a display unit provided in the frequency characteristic measuring device 10. It may be output to the outside of the characteristic measuring device 10 by communication.

The extraction unit 5 is implemented by installing a computer program for processing the measurement result of the first measurement unit and the measurement result of the second measurement unit in a computer such as a microcomputer, and executing the computer program. be able to. Although the extractor 5 is built in the frequency characteristic measuring device 10 in this embodiment, a computer provided outside the frequency characteristic measuring device 10 may function as the extractor 5 .

FIG. 4 is a flow chart showing an operation example of the extraction unit 5 . The extraction unit 5 first acquires the measurement result of the first measurement unit (step S10). Next, the extraction unit 5 acquires the measurement result of the second measurement unit (step S20). Note that, unlike the present embodiment, step S20 may be performed first and then step S10 may be performed, or step S10 and step S20 may be performed in parallel.

After obtaining the measurement result of the first measurement unit and the measurement result of the second measurement unit, the extraction unit 5 performs vector operation on the measurement result of the first measurement unit and the measurement result of the second measurement unit to obtain the S of the DUT. Parameters are extracted (step S30), and the flow operation ends.

Next, details of the processing in step S30 will be described. FIG. 5 is a diagram schematically showing S parameters of the first fixture P2. FIG. 6 is a diagram schematically showing the S-parameters of the second fixture P3. FIG. 7 is a diagram schematically showing S parameters of the second substrate SUB2.

Based on the left-right symmetry between the first fixture P2 and the second fixture P3, the extraction unit 5 sets S21A=S12B and S12A=S21B. In addition, the extraction unit 5 regards the reflection on the second substrate end face of each of the first fixture P2 and the second fixture P3 as less than or equal to the reflection on the end face of the second substrate SUB2. The reflection on each virtual split surface of the fixture P3 is not regarded as less than the reflection on the end surface of the second substrate SUB2. It should be noted that "the reflection on the second substrate end surface of each of the first fixture P2 and the second fixture P3 is considered to be equal to or less than the reflection on the end surface of the second substrate SUB2" means substantially or completely in the frequency range of the measurement range. In addition, the reflection on the second substrate end face of each of the first fixture P2 and the second fixture P3 should be regarded as less than the reflection on the end face of the second substrate SUB2. In other words, in the frequency range of the measurement range, the case where the reflection at the second substrate end surface of each of the first fixture P2 and the second fixture P3 is partially eliminated is higher than the reflection at the end surface of the second substrate SUB2. not a thing Then, the extraction unit 5 obtains the S-parameters of the first fixture P2 and the S-parameters of the second fixture P3 from the measurement results of the second measurement unit. Specifically, the S-parameters of the first fixture P2 and the S-parameters of the second fixture P3 are as follows.
(1) The amplitude of S11A (the S parameter indicating the reflection from the second substrate end surface of the first fixture P2) is a single first fixed value over the entire frequency range of the measurement range. (2) The phase of S11A is , zero over the entire frequency range of the measurement range (3) S22A=(S22C-S11A)/S12C
(4) S21A=(1−S11B ² ×S21C) ^0.5
(5) S12A=(1-S22A ² ×S12C) ^0.5
(6) S11B=(S11C-S11A)/S21C
(7) The amplitude of S22B (the S parameter indicating the reflection at the second substrate end face of the second fixture P3) is a single first fixed value over the entire frequency range of the measurement range. (8) The phase of S22B is , zero over the entire frequency range of the measurement range (9) S21B=S12A
(10) S12B=S21A

The extraction unit 5 subtracts the S-parameters of the first fixture P2 and the S-parameters of the second fixture P3 from the measurement results of the first measurement unit by vector calculation to obtain the S-parameters of only the DUT.

Measurement using the frequency characteristic measurement apparatus 10 does not require a short board instead of a DUT, an open board instead of a DUT, or a board on which a load is mounted instead of a DUT. Therefore, the frequency characteristic measuring apparatus 10 can easily measure the frequency characteristic of the DUT at low cost.

Assuming that the S-parameter S11A of the first fixture P2 has a value indicating low reflection, the S-parameter S11 of the first substrate SUB1 is almost determined by the S-parameter S11B of the second fixture P3 if the DUT has high transmission characteristics. Conversely, if the DUT has high reflection characteristics, the S-parameter S11 of the first substrate SUB1 is almost determined by the S-parameter S11 of the DUT. Although the two extreme cases of the DUT having high transmission characteristics and the DUT having high reflection characteristics have been described, even in other cases, the S parameter S11 of the first substrate SUB1 is the same as that of the second fixture P3. It is almost determined by the S parameter S11B and the S parameter S11 of the DUT.

Similarly, if the S-parameter S22B of the second fixture P3 is a value indicating low reflection, then the S-parameter S22 of the first substrate SUB1 will be the S-parameter S22A of the first fixture P2 if the DUT has high transmission characteristics. On the contrary, if the DUT has a high reflection characteristic, the S parameter S22 of the first substrate SUB1 is almost determined by the S parameter S22 of the DUT. Two extreme cases, that is, the case where the DUT has high transmission characteristics and the case where the DUT has high reflection characteristics, have been described. It is almost determined by the S parameter S22A and the S parameter S22 of the DUT.

In other words, it is reasonable for the extraction unit 5 to regard the reflection on the second substrate end surface of each of the first fixture P2 and the second fixture P3 as being below a predetermined level over the entire frequency range of the measurement range. is.

Similar to the frequency characteristic measuring apparatus 10, a measuring apparatus that does not require a short board instead of a DUT, an open board instead of a DUT, and a board on which a load is mounted instead of a DUT is called "Design criteria of automatic fixture removal (AFR) for asymmetric fixture dembeddining” (IEEE Conference Paper, p.654-p.659, August 2014). However, the first and second fixtures described in Fig. 2 of "Design criteria of automatic fixture removal (AFR) for asymmetric fixture dembeddining" (IEEE Conference Paper, p.654-p.659, August 2014) It is presumed that the virtual division with the channel cannot be properly executed unless the distance between the two end faces to which the cable of the second substrate SUB2 is connected is at least twice the reciprocal of the lowest frequency in the measurement range. On the other hand, in the frequency characteristic measuring apparatus 10, the distance between the two end faces to which the cable of the second substrate SUB2 is connected is the reciprocal of the lowest frequency in the measurement range in order to obtain each of the above S parameters (1) to (10). need not be more than twice the Therefore, from the viewpoint of miniaturization and cost reduction of the second substrate SUB2, it is preferable that the distance between the two end faces to which the cable of the second substrate SUB2 is connected is less than twice the reciprocal of the lowest frequency in the measurement range. preferable.

In the above-described embodiment, the extraction unit 5 assumed that the transmission characteristics of the first fixture P2 and the transmission characteristics of the second fixture P3 were symmetrical. It may not be assumed that the characteristics and the transmission characteristics of the second fixture P3 are symmetrical. If the extraction unit 5 does not consider that the transmission characteristics of the first fixture P2 and the transmission characteristics of the second fixture P3 are symmetrical, the above (9) changes to the following (9)′, and the above (10) becomes It changes to (10)' below.
(9) 'S21B=(1-S11B ² ×S21C) ^0.5
(10) 'S12B=(1-S22A ² ×S12C) ^0.5

In the above-described embodiment, the first substrate SUB1 has a structure including two connectors (the first connector CN1 and the second connector CN2). good.

That is, the first substrate SUB1 may have a structure in which at least one connector is provided on each of the first end surface and the second end surface. The second substrate SUB2 may have a structure in which the portion where the DUT is mounted is removed from the first substrate SUB1, and any two connectors are selected from among all the connectors provided on the first substrate SUB1 and through-connected. Just do it. The number of second substrates SUB2 is the total number of combinations in which two connectors are selected from all the connectors provided on the first substrate SUB1.

An outline of the measurement procedure will be described below, taking as an example the case where the first substrate SUB1 has a structure including four connectors (first to fourth connectors).

If the first substrate SUB1 has a structure with four connectors (first to fourth connectors), the number of second substrates SUB2 is six (= ₄ C ₂ ).

The first second substrate SUB2 has a structure in which the portion where the DUT is mounted is removed from the first substrate SUB1, and the first connector and the second connector provided on the first substrate SUB1 are through-connected.

The second substrate SUB2 has a structure in which the portion where the DUT is mounted is removed from the first substrate SUB1, and the first connector and the third connector provided on the first substrate SUB1 are through-connected.

The third second substrate SUB2 has a structure in which the portion where the DUT is mounted is removed from the first substrate SUB1, and through connection is made between the first connector and the fourth connector provided on the first substrate SUB1.

The fourth second substrate SUB2 has a structure in which the portion where the DUT is mounted is removed from the first substrate SUB1, and the second connector and the third connector provided on the first substrate SUB1 are through-connected.

The fifth second substrate SUB2 has a structure in which the portion where the DUT is mounted is removed from the first substrate SUB1, and the second connector and the fourth connector provided on the first substrate SUB1 are through-connected.

The sixth second substrate SUB2 has a structure in which the portion where the DUT is mounted is removed from the first substrate SUB1, and the third connector and the fourth connector provided on the first substrate SUB1 are through-connected.

As in the above-described embodiment, virtual division is performed for each of the first to sixth second substrates SUB2, and the S-parameters of the first fixture and the S-parameters of the second fixture are obtained. Using the fixture S-parameters and the second fixture S-parameters, the DUT-only S-parameters are determined.

Here, attention is focused on the first second substrate SUB2 and the second second substrate SUB2. The S parameters of the first fixture on the first second substrate SUB2 are S11A, S12A, S21A, and S22A. The S parameters of the second fixture on the first second substrate SUB2 are S11B, S12B, S21B, and S22B. The S parameters of the first fixture on the second second substrate SUB2 are S11A, S31A, S13A, and S33A. Also, the S parameters of the second fixture on the second substrate SUB2 are S11B, S31B, S13B, and S33B. Therefore, S11B is obtained from the first second substrate SUB2, and S11B is obtained from the second second substrate SUB2.

In this way, the diagonal components of the S parameters are obtained redundantly. Therefore, for each diagonal component obtained in duplicate, a criterion such as adopting the one with the largest reflection or averaging processing, for example, is set, and the value of each diagonal component is calculated based on the criterion. It is determined.

After the value of each diagonal component is determined, the value of each off-diagonal component may be calculated again. Then, the value of each off-diagonal component before recalculation is compared with the value of each off-diagonal component after recalculation, and for example, the one with the largest reflection is adopted as a criterion, or for example, average processing is performed. A criterion or the like is provided, and the value of each off-diagonal component is finally determined based on the criterion.

If the number of ports of the frequency characteristic measuring device is greater than the number of connectors of the first substrate SUB1, unused ports of the frequency characteristic measuring device may be terminated with 50Ω.

Reference Signs List 1 first port 2 second port 3 calibration unit 4 measurement unit 5 extraction unit 10 frequency specific measurement device according to one embodiment CN1 first connector CN2 second connector CX1 first coaxial cable CX2 second coaxial cable E11 first coaxial cable One end E12 The other end of the first coaxial cable E21 One end of the second coaxial cable E22 The other end of the second coaxial cable P1 Portion where DUT is mounted P2 First fixture P3 Second fixture SUB1 First substrate SUB2 Second substrate

Claims (6)

a calibration unit configured to perform a SOLT calibration at the cable end face;
a first measurement unit configured to measure S-parameters of a first substrate on which a DUT is mounted after the SOLT calibration by the calibration unit;
a second measurement unit configured to measure S-parameters of a second substrate after the SOLT calibration by the calibration unit;
an extraction unit configured to extract S-parameters of the DUT by performing vector operations on the measurement results of the first measurement unit and the measurement results of the second measurement unit;
with
The extracting unit does not virtually divide the second substrate into two at the center, the reflection of each of the first fixture and the second fixture obtained by virtually dividing the second substrate into two at the center. Considered as less than the reflection at the end surface of the second substrate in the case of
The first substrate has a structure in which at least one connector is provided on each of the first end face and the second end face,
The second substrate has a structure in which the portion where the DUT is mounted is removed from the first substrate, and two arbitrary connectors are selected from all the connectors provided on the first substrate and through-connected. ,
The frequency characteristic measuring device, wherein the number of second substrates is the total number of combinations in which two connectors are selected from all the connectors provided on the first substrate. The extractor is
The amplitude of the S parameter indicating the reflection at the end surface of the second substrate of the first fixture is set to a single first fixed value over the entire frequency range of the measurement range,
setting the phase of the S parameter indicating the reflection at the end surface of the second substrate of the first fixture to zero over the entire frequency range of the measurement range;
The amplitude of the S parameter indicating the reflection at the end surface of the second substrate of the second fixture is set to the first fixed value over the entire frequency range of the measurement range,
2. The frequency characteristic measuring apparatus according to claim 1, wherein the phase of the S parameter indicating the reflection of said second fixture at said second substrate end surface is set to zero over the entire frequency range of the measurement range. The extractor is
3. The frequency characteristic measuring apparatus according to claim 1, wherein the transmission characteristics of said first fixture and the transmission characteristics of said second fixture are assumed to be symmetrical. The extractor is
3. The frequency characteristic measuring apparatus according to claim 1, wherein the transmission characteristics of said first fixture and the transmission characteristics of said second fixture are not considered symmetrical. The frequency characteristic measuring device according to any one of claims 1 to 4, wherein the distance between two end faces to which the cable of the second substrate is connected is less than twice the reciprocal of the lowest frequency in the measurement range. a calibration unit configured to perform a SOLT calibration at the cable end face;
a first measurement unit configured to measure S-parameters of a first substrate on which a DUT is mounted after the SOLT calibration by the calibration unit;
a second measurement unit configured to measure S-parameters of a second substrate after the SOLT calibration by the calibration unit;
A computer program for processing measurement results of a frequency characteristic measuring device comprising
the computer,
a first acquisition unit that acquires the measurement result of the first measurement unit;
a second acquisition unit that acquires the measurement result of the second measurement unit; and a vector operation of the measurement result of the first measurement unit and the measurement result of the second measurement unit to extract the S-parameter of the DUT. function as an extractor composed of
The extracting unit does not virtually divide the second substrate into two at the center, the reflection of each of the first fixture and the second fixture obtained by virtually dividing the second substrate into two at the center. Considered as less than the reflection at the end surface of the second substrate in the case of
The first substrate has a structure in which at least one connector is provided on each of the first end face and the second end face,
The second substrate has a structure in which the portion where the DUT is mounted is removed from the first substrate, and two arbitrary connectors are selected from all the connectors provided on the first substrate and through-connected. ,
A computer program according to claim 1, wherein the number of second substrates is the total number of combinations in which two of all the connectors provided on the first substrate are selected.

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